Reversible-circulation internal fan kiln



June 9, 1925.

R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN Ori gina1FiledNov.7,l925

3 Sheets-Sheet 1 oomooooooooo E oooom oooooo S! 83 E g E 4 OOOOOOOQOOOGL y I 1 INVENTOIL Fjjrl @LF HELE? Y MW ATTORNEY- June 9, 1925. 1,541,444

- R. THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN Originl Filed Nov.'7, 1923 3 Sheets-Sheet 2 -m-mm INVENTOR. ROLF IHELEN BY ATTORNEYS.

June 9, 1925. 1,541,444

R.- THELEN REVERSIBLE CIRCULATION INTERNAL FAN KILN Original Filed Nov.v, 1923 3 SheetsSheet s Fig. -5

-INVEN50R. RoLFIHsLEN BYWWW- ATTORNEYS.

Patented June '9, 1925.

UNITED STATES ROLF THELEN, OF MADISON, WISCONSIN,

DEDICATED, ,BY MESNE ASSIGNMENTS, TO

PATE

THE CITIZENS OF THE UNITED STATES OF AMERICA.

REVERSIBLE-CIRCULATION INTERNAL FAN KI'LN.

Original application filed November 7, 1923, Serial No. 673,340. Dividedand this application filed 1 March 7, 1925. -Ser1a1 No. 14 ,425.

(GRANTED UNDER THE ACT OF MARCH 3, 1883; 22 STAT. I1. 625.)

I To all whom it mayconcern: i

' Be it known that I, RoLr THELEN, a citizen of the United States ofAmerica, and an employee of the Department of Agriculture, 5 residing inMadison, Wisconsin (whose postoflice address is Madison, Wisconsin),have invented a new and Improved Reversible- Circulation Internal FanKiln.

I This application is a division of an application filed November 7,1923, which bears Serial Number 673,340. a

This application is made under the act of March 3, 1883, chapter 143 (22Stat. 625), and the invention herein desgribed and claimed may be usedby the Government of the United States, its oflicers and employees, andby any person in the United States without the payment'to me of anyroyalty there on. I hereby dedicate the same to the'free use of theGovernment and the people of the United States. I

My invention consists in an improvement inthe design of forcedcirculation kilns or chambers for drying and conditioning lum- 25 her orsimilar material. However, its use is not limited to wood or woodproducts. It consists in the adaptation of fans of the disk type, orsimilar types, to the production of a unique internal circulation of airand the vapor in the kiln combined with the production and regulation ofthe heat and the humidity within the kiln.

This invention is illustrated in Figures 1 to 3. Figure 1 represents across-sectional elevation. Figure 2 represents a horizontalcross-section taken at varying levels near the base. Figure 3 is avertical longitudinal section showing some of the fan details.

The principal feature which I claim as novel and an improvement overexisting kilns is the use and arrangement of the fans and the airdistributing system. This arrangement is such that avery fast anduniform circulation of air and vapor through the piles of lumber may besecured and it permits the tion of the air movement by simplyreyersing'the direction of rotation of the fans.

The air distributing system provides a very uniform flow of airthroughout the length.

and breadth of the kiln and eliminates the non-uniformity of drying,which is one of eriodic reversal of the directhe commonest troublesexperienced in the ordinary kiln. I The arrangement of the fans upon twoparallel shafts extending throughout the length of the kiln provides asimple means'of producing a brisk circulation; and the elimination ofcomparatively small ducts such as those used in external blower kilnsreduces very materially the work required to produce a givencirculation. The differences in air pressure'required in the operationof this kiln are much smaller than those ordinarily required in kilnsemploying cen trifugal blowers, and the disk fans 0 crate veryefliciently at these low pressures. easurements recently made indicatethat the static pressures necessary for the successful operation of thissystem are materially less than one-eighth of an inch of water'pressure. It is possible, therefore, by the use of this invention toproduce a very great and uniform circulation of air and vapor within thekiln with a very small expenditure of power.

While it is obvious that there are many possible ways in which the useof internal fans can be adapted to dry kilns of difl'erent types, thisinvention -is limited to single track, kilns in which the lumber is edgestacked. In edge stacked lumber the width of each board is in a verticaldirection, the

thickness and length being in horizontal directions.

-An y well-known means of heating the air and the vapor in the kiln maybe used in conjunction with this invention. When steam pipes are usedthey may be arranged beneath the lumber piles at the sides of the kilnor in any other convenient manner. Any convenient. form and arrangementof heaters may be used. I

The drawings show and the specification describes steam jet pipes forincreasing the humidityfand air inlet flues and air outlet fiues withsuitable dampers for decreasing the humidity. I

While the drawings show and the specification describes specific meansfor heat the air and the vapor in the kiln and for regulating thehumidity of the air in the kiln, ,this invention is not limitedspecifically to the arrangements described, but may make use of anyother well-known and suitable means for accomplishing the same purposes.I While the drawings illustrate and the speci- 'fication describescertain specific forms of piling, the invention is not limited to theseparticular forms since it is equally applicable to other forms; neitheris the invention limited to the specific form of rails, trucks, andtrack supports illustrated in the drawin s and described in thespecification.

eferring to Figures 1, 2," and 3, which are correspondingly lettered: AArepresent the side deflecting partitions. These partitions serve to forma passageway for the air from the spaces at the sides of the kiln to thefans and vice versa, the air moving in a more or less horizontaldirection either inward towards the fans or outward from them, dependingupon the direction of the rotation of the fans. BB are the fansproducing the circulation. Straightbladed disk fans are preferable. Anytype of fan, however, in which the reversal of the direction of rotationof the fan produces a reversal in the direction of the flow of the aircurrent passing through the fan can be used. CC are the shafts uponwhich the fans are mounted. Provision is made to take care oftheexpansion and contraction of these shafts with changes in thetemperature in the kiln, and to take care of the thrust of the fans.This provision con-- sists in equipping one of the bearings, II, withsuitable thrust rings or collars and equipping all of the otherbearings, II, on each shaft with any well known means tor armature.While the drawings show and the. specification describes an electricmotor, any other suitable driving means ()0 are fitted. W W are the sideair passages between the piles of lumber and the side walls of the kiln.X is the main air distributor. YY are the upper diffusers. ZZ are thelower diffusers. The plenum chambers between the upper diffusers and thelower diffusers are the secondary plenum chambers. bb are the fanhousings and partitions. .ee are the return diffusers.

The operation of the kiln is briefly as follows: The lumber is placed inthe kiln, the doors and all of the dampers are closed, and the kiln isstarted. Steam' is turned into the coils and the steam jets are turnedon. vided to control and regulate the supply of steam to the heatingcoils and the.supply of steam to the steam jets. If it is foundimpossible to reduce the humidity to the desired point with the steam'ets all turned off, the dampers DD and O are opened to allow fresh airto enter and moist air to escape. These dampers should be adjusted sothat a humidity below that desired will be secured. The steam jets maythen supply a sufiicient amount of steam to brin the humidity up to thedesired point. if the direction of rotation of the for longitudinalmotion. ,Plain bearings? fans is such that the air and vapor pass androller bearings require no special provision of this kind. Certain typesof ballbearings require housings which permit the entirebearing to slidelongitudinally within them. DD are air inlet dampers used to regulateand control the amount of air entering the kiln from the outside. EF.are the heating coils These may be of the return bend type or other.convenient type. FF are the steam jet pipes used to increase thehumidity of the air in the kiln. Suitable openings are provided topermit the escape of the steam throughout the length of the kiln.Various other common and well-known arrangements may be used. GGrv arethe lumber-supporting trucks. I-II-I are the shaft hangers. II arebearings-for the shafts CC. JJ are the tracks upon which thelumber-supporting trucks run. KK are the side walls of the kiln. LL isthe lumber to be dried. MM are the track supports. NN are the shaftpulleys. are air outlet dampers for controlling the amount of air beingexhausted. from the kiln. PP are the belts passing over the pulleys NNand Q. Q is the motor pulley. R is the motor which furnishes the powerto drive the fans. S is a switch for controlling the speed and rotationof the moupward through the piles of lumber, the movementis as follows:From the fans BB it passes laterall to the right and the left past theside de ecting partitions AA, over the heating coils EE, which arelocated in the main air distributor X, which will be un der slightpressure and will act asa plenum chamber. The air and vapor pass upwardfrom this plenum chamber through the lower diffusers ZZ which may be ina single row or in two rows as illustrated, into the sec- W ondaryplenum chambers, and finally through the upper diffusers YY verticallythrough the lumber piles, horizontally outward between the tops of thelumber piles and the ceiling. of the kiln downward through. the side airpassages WW, past the return diflusers ee, thence to the fans BB,repeating the cycle continuously. When the direction of rotation of thefans is reversed, the direction of travel of the air and vapor islikewise reversed. The use of the two sets of difi'users in the mannerindicated produces a very uniform flow of airthrough the length of thekiln. The unbalancing effect of the'horiz'ontal air flow produced by thefans is practically eliminated by allowing a sli ht pressure to build upin the main air distributor. This is still further eliminated by theslight plenum in the space between the upper and lower dis tributors. Itis obvious that the kiln would work reasonably well with single sets ofdiffusers for each main air distributor and that still furtheruniformity in air distribution might be secured by adding a thirzl orevenra fourth set of diffusers. The principle, of course, remains thesame and practical expediency will determine the balance betweenincreased uniformity of air distribution secured by the addition of moresets of distributors and the loss in efi'iciencywhich they cause. It isalso obvious that any well-known form of distributor may be used. Theinvention is not restricted to the form illustrated in which theopenings consist simply of spaces between the slats running the 'fulllength of the kiln.

When the direction of air circulation is downward through the lumberpiles, the air distributing system, which consists of the main airdistributor, the side deflecting partitions, the plenum chamber, and theupper and lower diffusers, does not materially assist in producing auniform air circulation. The comparatively great length of air travelfrom the fans to the point at which the air enters the lumber and thereturn diffusers ee have been found suflicient to produce the desireduniformity. It has been found through experience with a great manydifferent types of forced circulation in dry kilns that it is notpossible to secure uniformity of air distribution. if the air behandledat high velocities. In order produce uniform satisfactorycirculation 1t is essential that the air be moved at low Velocities andthat special means be provided for the uniform distribution of the airthroughout the kiln. Theuse ofinternal fans and large lenum chambersproduces this result since the velocity of the air through the fansthemselves. is comparatively low and the velocity within the plenumchambers is so small that the velocity head cannot be measured withmanometers and similar instruments usually used for the purpose.

It is well understood that when the circulation of the air and the vaporin the kiln is continuously in one direction, that portion of the pileat which'the air enters will dry more rapidly than the opposite sidesince the air in its passage through the lum- -ber picks up moisture andthus reduces its drying capacity.' The reversal of the direction of theair circulation overcomes this defect since that edge of each lumberpile,

dried fastest before reversal dry most slowly after reversal. Thereversal of the circulation will in practice be done periodically everytwo or three days or oftener, the exacl. period being determined by thecondioriginal a 1. In a single track dry kiln arranged for edgestacking: two series of fans; two shafts on which the fans aremountedfor rotation; means for rotating said shafts in either directionto cause reversal of the circulation of the air and vapor in said kiln;and an air distributing system comprising side deflecting partitions, amain air distributor, and two sets of diffusers.

2. In a single track dry kiln arranged for edge stacking: two series offans; two shafts on which the fans are mounted for rotation; means forrotating said shafts in either direction to cause reversal ofthecirculation of the air and, vapor in said kiln; dampered air inletflues and dampered air outlet flues; and an air distributing systemcomprising side deflecting partitions, a main air distributor, and twosets of diffusers.

3. In a single track dry kiln arranged for edge stackin two series offans, two shafts on whlchthe fans are mounted for rotation; means forrotating said shafts in either direction to cause reversal of thecirculation of the air and vapor in said kiln; dampered air inlet fluesand dampered air outlet flues; means for heating the kiln and itscontents; and an air distributing system comprising side deflectingpartitions, a main air distributor, and'two sets. of diffusers.

4. In a single track dry kiln arranged for I edge stacking: twoseries offans; two shafts on which the, fans are mounted for rotation; means forrotating said shafts in either direction to cause reversal of thecirculation of the air and vapor in said kiln; dampered air inlet fluesand dam ered air outlet flues; means for heatin the 'ln and itscontents; means for humi ifying the atmosphere in the kiln; and an airdistributing system comprising side deflecting partitions, a main airdistributor, and two sets of diffusers.

5. In a single track dry kiln arranged for edge stacking: two series offans; two shafts on which the fans are mounted forrotation; means forrotating said shafts in either direction to cause reversal of thecirculation of the air and va. or in said kiln; a lenum chamber for ear:pair of fans; and a 'fi'user Ill] ' with restricted discharge passagesfor each plenum chamber.

6. In a single track dry kiln arranged for edge stacking: two series offans; two shafts on which the fans are mounted for rotation; means forrotating said shafts in either direction to cause reversal of thecirculation of the air and vapor in said kiln; dampered air inlet fluesand dampered. air outlet flues; a plenum chamber for each pair of fans;and a difl'user with restricted discharge passages for each plenumchamber.

7 In a single track dry kiln arranged for edgestacking: two series offans; two shafts on which the fans are mounted for rotation;

means for rotating said shafts in either d'i- Qrection to cause reversalof the circulation air inlet flues and dampered air" outlet fiues;

means for heating the kiln and its contents; means for humidifyingthe'atmosphere in the kiln; a plenum chamber for each pair of fans; andadilfuser with restricted discharge passages for each plenum chamber.

9. In a single track dry kiln arranged for edge stacking: two series offans; two shafts on which the fans are mounted for, rotation; means forrotating said shafts in either direction to cause reversal of thecirculation of the air and 'va or in said kiln; a series of plenum chamers for each air of fans; and a diffuser with restricted scharge passages for each plenum chamber.

7 10. In a single track dry kiln arranged for of fans; and a diffuserwith restricted discharge passages for each plenum chamber.

11. In a single track'dry kiln arranged for edge stacking: two series offans; two shafts on which the fans are mounted for rotation; means forrotating said shafts in either direction to cause reversal of thecirculation of the air and vapor in said kiln; dampered air inlet fluesand dampered air outlet flues; means for heating the kiln and itscontents; a series of plenum chambers for each pair of fans; andaidifi'user with restricted discharge passages for each plenum chamber.

12. In a single track dry kiln arranged for edge stacking: two series offans; two shafts on which the fans are mounted for rotation;

means for rotating said shafts in either direction to cause reversal ofthe circulation of the air and vapor in said kiln; dampered air inletflues and dampered air outlet fines; means for heatin the kiln and itscontents; means for humi ifying the atmos here in the-kiln; a series ofplenum cham' ers for each pair of fans; and a diffuser with restricteddischarge passages for each plenum chamber. a

13. In a single track dry kiln arranged for edge stacking: two series ofinternal fans; a plenum chamber for each air of fans; and a diffuserwith restricted discharge passages for each plenum chamber.

14. In a single track dry kiln arranged for edge stacking: two series ofinternal fans; a series of lenum chambers for each pair of fans; ancharge passages for each plenum chamber.

February 12 1925.. I

ROLF THELEN.

a difi'user with restricted dis-

